Aspects of the present invention are directed to an apparatus and method for dynamic mode nano-scale imaging and position control using deflection signal direct sampling of higher mode-actuated microcantilevers.
Scanning probe microscopy (SPM) based techniques have many practical applications such as mask-less lithography, semiconductor metrology and ultra-high density data storage. However, low throughput and durability have to be overcome before such applications can become widespread. One way to improve the throughput and the durability of probe-based devices is to employ a large number of parallel microcantilevers that are mass-fabricated as a microelectromechanical-systems (MEMS) device. In spite of such massive parallelism, tip-wear and sample damage in MEMS-SPM devices can be significant.
In parallel SPM applications, available electronic resources per microcantilever are limited. In contact mode (CM) SPM methods, images are captured by direct sampling of the microcantilever deflection signal. Due to its low cost of implementation, CM operation is typically employed in parallel SPM applications. On a similar note, in high-speed SPM applications, one of the reasons for CM imaging being employed is the constraint on electronic resources. However, such CM operations can distort the sample surface and wear the microcantilever's tip.
Recently, in order to decrease the tip-wear, tip-sample force was modulated at a very high frequency while operating in CM. While this demonstrated significant wear reduction, this scheme has only been applied to polymer samples and it is unclear that it would perform as well on non-polymer samples. It is also unclear what impact the modulating would have on the sample's properties.
Compared to such CM schemes, intermittent-contact (IC) operations impose less wear on both the microcantilever and the sample and include, for example, tapping mode (TM) operations, which have reported reduced tip and sample wear. However, TM and similar IC methods require demodulation electronics to extract the amplitude, phase and frequency information of microcantilever oscillation and, as such, add cost and fabrication complexity. Such IC methods are, therefore, less attractive for many parallel SPM applications.